fix: output mjs and ts v2 functions with mjs extension (#1505)

* fix: output mjs and ts v2 functions with mjs extension

* feat: use right extension for TS files

* chore: formatting

* chore: update paths in tests

* chore: update paths in test

* refactor: rename variable

* refactor: remove unnecessary check

* chore: update test

* chore: rename variable

* feat: ensure `package.json` with `type: "module"`

* refactor: move logic to ZIP generator

* refactor: reuse common method

* chore: restructure code

* feat: read tsconfig

* chore: hello

* refactor: revert abstraction

* chore: add comment

* chore: update vitest config

* refactor: revert default value

* fix: account for CJS and ESM entry files

* feat: plant `package.json`

* chore: add placeholder tsconfig

* refactor: remove check for ESM

* fix: emit ESM for `es6` and `es2015`

* feat: set boundary to `tsconfig.json`

* feat: add boundary for `package.json` search

---------

Co-authored-by: Eduardo Bouças <mail@eduardoboucas.com>

.eslintrc.cjs

@@ -53,5 +53,5 @@ module.exports = {
       },
     },
   ],
-  ignorePatterns: ['tests/fixtures/**/*'],
+  ignorePatterns: ['tests/fixtures/**/*', 'tests/fixtures-esm/**/*'],
 }

package.json

@@ -66,6 +66,7 @@
     "execa": "^6.0.0",
     "filter-obj": "^5.0.0",
     "find-up": "^6.0.0",
+    "get-tsconfig": "^4.6.2",
     "glob": "^8.0.3",
     "is-builtin-module": "^3.1.0",
     "is-path-inside": "^4.0.0",

src/runtimes/node/bundlers/esbuild/bundler.ts

@@ -107,18 +107,18 @@ export const bundleJsFile = async function ({
   })
 
   // The extension of the output file.
-  const outputExtension = getFileExtensionForFormat(moduleFormat, featureFlags)
+  const outputExtension = getFileExtensionForFormat(moduleFormat, featureFlags, runtimeAPIVersion)
 
   // We add this banner so that calls to require() still work in ESM modules, especially when importing node built-ins
   // We have to do this until this is fixed in esbuild: https://github.com/evanw/esbuild/pull/2067
   const esmJSBanner = `
-    import {createRequire as ___nfyCreateRequire} from "module";
-    import {fileURLToPath as ___nfyFileURLToPath} from "url";
-    import {dirname as ___nfyPathDirname} from "path";
-    let __filename=___nfyFileURLToPath(import.meta.url);
-    let __dirname=___nfyPathDirname(___nfyFileURLToPath(import.meta.url));
-    let require=___nfyCreateRequire(import.meta.url);
-  `
+import {createRequire as ___nfyCreateRequire} from "module";
+import {fileURLToPath as ___nfyFileURLToPath} from "url";
+import {dirname as ___nfyPathDirname} from "path";
+let __filename=___nfyFileURLToPath(import.meta.url);
+let __dirname=___nfyPathDirname(___nfyFileURLToPath(import.meta.url));
+let require=___nfyCreateRequire(import.meta.url);
+`
 
   try {
     const { metafile = { inputs: {}, outputs: {} }, warnings } = await build({

src/runtimes/node/bundlers/nft/es_modules.ts

@@ -5,13 +5,10 @@ import { NodeFileTraceReasons } from '@vercel/nft'
 import type { FunctionConfig } from '../../../../config.js'
 import { FeatureFlags } from '../../../../feature_flags.js'
 import type { RuntimeCache } from '../../../../utils/cache.js'
-import { FunctionBundlingUserError } from '../../../../utils/error.js'
 import { cachedReadFile } from '../../../../utils/fs.js'
-import { RUNTIME } from '../../../runtime.js'
 import { ModuleFormat, MODULE_FILE_EXTENSION, MODULE_FORMAT } from '../../utils/module_format.js'
 import { getNodeSupportMatrix } from '../../utils/node_version.js'
 import { getPackageJsonIfAvailable, PackageJson } from '../../utils/package_json.js'
-import { NODE_BUNDLER } from '../types.js'
 
 import { transpile } from './transpile.js'
 
@@ -83,20 +80,7 @@ export const processESM = async ({
     }
   }
 
-  const entrypointIsESM = isEntrypointESM({ basePath, esmPaths, mainFile })
-
-  if (!entrypointIsESM) {
-    if (runtimeAPIVersion === 2) {
-      throw new FunctionBundlingUserError(
-        `The function '${name}' must use the ES module syntax. To learn more, visit https://ntl.fyi/esm.`,
-        {
-          functionName: name,
-          runtime: RUNTIME.JAVASCRIPT,
-          bundler: NODE_BUNDLER.NFT,
-        },
-      )
-    }
-
+  if (!isEntrypointESM({ basePath, esmPaths, mainFile })) {
     return {
       moduleFormat: MODULE_FORMAT.COMMONJS,
     }
@@ -111,17 +95,6 @@ export const processESM = async ({
     }
   }
 
-  if (runtimeAPIVersion === 2) {
-    throw new FunctionBundlingUserError(
-      `The function '${name}' must use the ES module syntax. To learn more, visit https://ntl.fyi/esm.`,
-      {
-        functionName: name,
-        runtime: RUNTIME.JAVASCRIPT,
-        bundler: NODE_BUNDLER.NFT,
-      },
-    )
-  }
-
   const rewrites = await transpileESM({ basePath, cache, config, esmPaths, reasons, name })
 
   return {

src/runtimes/node/bundlers/nft/index.ts

@@ -10,8 +10,9 @@ import { cachedReadFile, getPathWithExtension } from '../../../../utils/fs.js'
 import { minimatch } from '../../../../utils/matching.js'
 import { getBasePath } from '../../utils/base_path.js'
 import { filterExcludedPaths, getPathsOfIncludedFiles } from '../../utils/included_files.js'
-import { MODULE_FORMAT } from '../../utils/module_format.js'
+import { MODULE_FORMAT, MODULE_FILE_EXTENSION, tsExtensions } from '../../utils/module_format.js'
 import { getNodeSupportMatrix } from '../../utils/node_version.js'
+import { getModuleFormat as getTSModuleFormat } from '../../utils/tsconfig.js'
 import type { GetSrcFilesFunction, BundleFunction } from '../types.js'
 
 import { processESM } from './es_modules.js'
@@ -49,6 +50,7 @@ const bundle: BundleFunction = async ({
     mainFile,
     pluginsModulesPath,
     name,
+    repositoryRoot,
     runtimeAPIVersion,
   })
   const includedPaths = filterExcludedPaths(includedFilePaths, excludePatterns)
@@ -91,6 +93,7 @@ const traceFilesAndTranspile = async function ({
   mainFile,
   pluginsModulesPath,
   name,
+  repositoryRoot,
   runtimeAPIVersion,
 }: {
   basePath?: string
@@ -100,9 +103,11 @@ const traceFilesAndTranspile = async function ({
   mainFile: string
   pluginsModulesPath?: string
   name: string
+  repositoryRoot?: string
   runtimeAPIVersion: number
 }) {
-  const isTypeScript = extname(mainFile) === '.ts'
+  const isTypeScript = tsExtensions.has(extname(mainFile))
+  const tsFormat = isTypeScript ? getTSModuleFormat(mainFile, repositoryRoot) : MODULE_FORMAT.COMMONJS
   const tsAliases = new Map<string, string>()
   const tsRewrites = new Map<string, string>()
 
@@ -118,9 +123,11 @@ const traceFilesAndTranspile = async function ({
     ignore: getIgnoreFunction(config),
     readFile: async (path: string) => {
       try {
-        if (extname(path) === '.ts') {
-          const transpiledSource = await transpile({ config, name, path })
-          const newPath = getPathWithExtension(path, '.js')
+        const extension = extname(path)
+
+        if (tsExtensions.has(extension)) {
+          const transpiledSource = await transpile({ config, name, format: tsFormat, path })
+          const newPath = getPathWithExtension(path, MODULE_FILE_EXTENSION.JS)
 
           // Overriding the contents of the `.ts` file.
           tsRewrites.set(path, transpiledSource)
@@ -131,9 +138,7 @@ const traceFilesAndTranspile = async function ({
           return transpiledSource
         }
 
-        const source = await cachedReadFile(cache.fileCache, path)
-
-        return source
+        return await cachedReadFile(cache.fileCache, path)
       } catch (error) {
         if (error.code === 'ENOENT' || error.code === 'EISDIR') {
           return null
@@ -166,8 +171,8 @@ const traceFilesAndTranspile = async function ({
   if (isTypeScript) {
     return {
       aliases: tsAliases,
-      mainFile: getPathWithExtension(mainFile, '.js'),
-      moduleFormat: MODULE_FORMAT.ESM,
+      mainFile: getPathWithExtension(mainFile, MODULE_FILE_EXTENSION.JS),
+      moduleFormat: tsFormat,
       paths: normalizedDependencyPaths,
       rewrites: tsRewrites,
     }

src/runtimes/node/index.ts

@@ -83,7 +83,7 @@ const zipFunction: ZipFunction = async function ({
     moduleFormat,
     nativeNodeModules,
     nodeModulesWithDynamicImports,
-    rewrites,
+    rewrites = new Map(),
     srcFiles,
   } = await bundler.bundle({
     basePath,
@@ -117,6 +117,8 @@ const zipFunction: ZipFunction = async function ({
     filename,
     mainFile: finalMainFile,
     moduleFormat,
+    name,
+    repositoryRoot,
     rewrites,
     runtimeAPIVersion,
     srcFiles,

src/runtimes/node/utils/entry_file.ts

@@ -32,8 +32,12 @@ const getEntryFileContents = (
   if (runtimeAPIVersion === 2) {
     return [
       `import * as func from '${importPath}'`,
-      `import { getLambdaHandler } from './${BOOTSTRAP_FILE_NAME}'`,
-      `export const handler = getLambdaHandler(func)`,
+      `import * as bootstrap from './${BOOTSTRAP_FILE_NAME}'`,
+
+      // See https://esbuild.github.io/content-types/#default-interop.
+      'const funcModule = typeof func.default === "function" ? func : func.default',
+
+      `export const handler = bootstrap.getLambdaHandler(funcModule)`,
     ].join(';')
   }
 
@@ -167,7 +171,7 @@ export const getEntryFile = ({
   runtimeAPIVersion: number
 }): EntryFile => {
   const mainPath = normalizeFilePath({ commonPrefix, path: mainFile, userNamespace })
-  const extension = getFileExtensionForFormat(moduleFormat, featureFlags)
+  const extension = getFileExtensionForFormat(moduleFormat, featureFlags, runtimeAPIVersion)
   const entryFilename = getEntryFileName({ extension, featureFlags, filename, runtimeAPIVersion })
   const contents = getEntryFileContents(mainPath, moduleFormat, featureFlags, runtimeAPIVersion)
 

src/runtimes/node/utils/module_format.ts

@@ -1,6 +1,8 @@
 import type { FeatureFlags } from '../../../feature_flags.js'
 import { ObjectValues } from '../../../types/utils.js'
 
+export const tsExtensions = new Set(['.ts', '.cts', '.mts'])
+
 export const MODULE_FORMAT = {
   COMMONJS: 'cjs',
   ESM: 'esm',
@@ -19,8 +21,9 @@ export type ModuleFileExtension = ObjectValues<typeof MODULE_FILE_EXTENSION>
 export const getFileExtensionForFormat = (
   moduleFormat: ModuleFormat,
   featureFlags: FeatureFlags,
+  runtimeAPIVersion: number,
 ): ModuleFileExtension => {
-  if (moduleFormat === MODULE_FORMAT.ESM && featureFlags.zisi_pure_esm_mjs) {
+  if (moduleFormat === MODULE_FORMAT.ESM && (runtimeAPIVersion === 2 || featureFlags.zisi_pure_esm_mjs)) {
     return MODULE_FILE_EXTENSION.MJS
   }
 

src/runtimes/node/utils/package_json.ts

@@ -22,7 +22,7 @@ export interface PackageJsonFile {
   path: string
 }
 
-export const getClosestPackageJson = async (resolveDir: string): Promise<PackageJsonFile | null> => {
+export const getClosestPackageJson = async (resolveDir: string, boundary?: string): Promise<PackageJsonFile | null> => {
   const packageJsonPath = await findUp(
     async (directory) => {
       // We stop traversing if we're about to leave the boundaries of any
@@ -36,7 +36,7 @@ export const getClosestPackageJson = async (resolveDir: string): Promise<Package
 
       return hasPackageJson ? path : undefined
     },
-    { cwd: resolveDir },
+    { cwd: resolveDir, stopAt: boundary },
   )
 
   if (packageJsonPath === undefined) {

src/runtimes/node/utils/tsconfig.ts

@@ -0,0 +1,27 @@
+import { dirname, relative } from 'path'
+
+import { getTsconfig } from 'get-tsconfig'
+
+import { MODULE_FORMAT } from './module_format.js'
+
+const esmModuleValues = new Set(['es6', 'es2015', 'es2020', 'es2022', 'esnext', 'node16', 'nodenext'])
+
+// Returns the module format that should be used for a TypeScript file at a
+// given path, by reading the associated `tsconfig.json` file if it exists.
+export const getModuleFormat = (path: string, boundary?: string) => {
+  const file = getTsconfig(path)
+
+  if (!file) {
+    return MODULE_FORMAT.COMMONJS
+  }
+
+  // If there is a boundary defined and the file we found is outside of it,
+  // discard the file.
+  if (boundary !== undefined && relative(boundary, dirname(file.path)).startsWith('..')) {
+    return MODULE_FORMAT.COMMONJS
+  }
+
+  const moduleProp = file.config.compilerOptions?.module?.toLowerCase() ?? ''
+
+  return esmModuleValues.has(moduleProp) ? MODULE_FORMAT.ESM : MODULE_FORMAT.COMMONJS
+}